1. Field of the Invention
The invention relates to zoom viewfinder systems. Such systems are useful in photographic cameras.
2. Description Relative to the Prior Art
Cameras using zoom lens systems are well known. In such cameras viewing of the scene by the operator is facilitated by providing a viewfinding device, i.e., a viewfinder that allows the operator to view the object whose image is being recorded by the camera. In those cameras providing through the lens reflex viewing, the image of the object is viewed immediately prior to exposure by using a mirror which is moved before exposure of the film. Camera cost savings may be realized by eliminating the reflex viewing system. However, a need arises to provide a viewing system separate from the exposing system and to have said viewing system be provided with the ability to continuously vary the angular field of view, popularly referred to as zooming. Heretofore, zoom viewfinders of the Galillean type have been suggested. However, because zoom viewfinders of the Galillean type become increasingly large and complex when designed to the 2:1 and greater variable power range and because they have a poorly delineated field of view, other known systems consisting of a zooming objective as the first portion followed by an eyepiece have been developed. While these other systems can be designed for large variable power ranges, they also can become large and complex because of the need for an erecting means. Other systems also employ field lenses to redirect light near the edge of the field of view into the exit (i.e., viewing) pupil. If the field lens is not used, only light from the central portion of the image will reach the eye. U.S. Pat. No. 4,972,216 describes a camera having a real image viewfinder. The disclosed viewfinder has a front optical unit serving as an objective lens, a second optical unit that is a reflective assembly and a third optical unit serving as an eyepiece. The patent does not disclose a field lens. Without a field lens, as the user of the camera looks at the real image, the edges of the field of view appear dim and fade away. The field lens would correct this problem but it represents an extra element and, thus, additional complexity and cost to the lens system.